NiMH and NiCd charge voltage limit

[Paweł Si]

2015-01-18 16:33 GMT+01:00 SileNTViP SileNTViP <silen...@gmail.com>:

 Hi Pawel. 

How about NiCD and max Voltage? 1.820 by default. It can be like a NiMH 1.620?

currently we have:

NiCd charge voltage limit: 1.82V

NiMH charge voltage limit: 1.6V

you mean I should set NiCd voltage limit to 1.62V?

hmm...

Now I'm not even sure now if the NiMH voltage limit should be 1.6V

according to this:

http://eu.industrial.panasonic.com/sites/default/pidseu/files/downloads/files/ni-mh-handbook-2014_interactive.pdf

for NiMH batteries it should be 1.8V/cell

If you have any reliable source please let me know.

(I have the 1.82V value from http://www.fuw.edu.pl/~jt/akumulatorki.html,

unfortunately it's in polish, the value was taken from an old book,

I don't treat it as a very reliable)

Some words about the voltage limit for NiCd, NiMH:

1. this limit is only a safety limit, it should never occur

2. if the charging process ends with: "reason: V limit"

    then there is something wrong with the charging

Best Regards,

Paweł

[SileNTViP SileNTViP]

Hi Pawel.
Interesting... http://www.atmel.com/Images/doc8098.pdf

[SileNTViP SileNTViP]

And...
http://www.powerstream.com/NiMH.htm
http://na.industrial.panasonic.com/sites/default/pidsa/files/panasonic_nimh_chargemethods.pdf

[JagiChan Sir]

Interesting articles about NiMH charging. The panasonic website has tons of info on various batteries. Thanks for the find and sharing.

[Paweł Si]

2015-01-20 21:27 GMT+01:00 SileNTViP SileNTViP <silen...@gmail.com>:

Hi Pawel.
Interesting... http://www.atmel.com/Images/doc8098.pdf

Very nice article, there is also code available for it,

I've checked the voltage limits:

NIMHspecs.h:51

#define CELL_VOLTAGE_MAX     1600

so it's like in cheali-charger,

although if someone would like to charge a NIMH in 0°C temperature

Hi will have problems (but I think we can live with that).

remarks:

cheali-charger implements 2 of the 3 stages presented in this article,

we don't have the 3-rd stage: "Top up the battery with a low current (0.1 C)",

(if some is interested in implementing it, I'm ready to help),

we also use -dV and -dT/dt methods to determine end of charging.

hmm...

I must admit that I don't like this kind of articles, 

there are some interesting parts, for example:

"There are new algorithms that use microprocessor control to use the -dV signal to detect the end of charge. These can work very well and several of our chargers use this technique, which involves pulsing the charger on and off to do the voltage measurements. "

but they are not informative... where are the details?

Best Regards,

Paweł

[Владимир Залогин]

Hello Pawel!

I fixed the second IMAX, burn only transistor. But is not the point, I charge and discharge 5 different capacity NIMH battery, charge all the stops to 1,58V 1,56V. All stops were dv = 5V. I mean the limit 1,6V is enough. And another proposal, can be made, in profile NIMH, made default value of deltaV = 0,1C, not C as in LiIon profile? 

[Владимир Залогин]

Sorry. I mean deltaV=5mV

среда, 21 января 2015 г., 20:47:39 UTC+3 пользователь Владимир Залогин написал:

[JagiChan Sir]

remarks:

cheali-charger implements 2 of the 3 stages presented in this article,

we don't have the 3-rd stage: "Top up the battery with a low current (0.1 C)",

(if some is interested in implementing it, I'm ready to help),

we also use -dV and -dT/dt methods to determine end of charging.

Yes, I'm interested to implement the same. Will help me learn C++ :)

 

"There are new algorithms that use microprocessor control to use the -dV signal to detect the end of charge. These can work very well and several of our chargers use this technique, which involves pulsing the charger on and off to do the voltage measurements. "

but they are not informative... where are the details?

What details are you looking for? At my current organization we work on the 480V battery chargers for Hybrid Cars (that's too much of voltage than my B6 can handle) :)

Regards,

JagiChan 

[JagiChan Sir]

There is a nice website called battery university... the link is here. A lot of info about batteries is in here.... I'm still exploring the site.

[Igon]

 I charge and discharge 5 different capacity NIMH battery, charge all the stops to 1,58V 1,56V. All stops were dv = 5V. I mean the limit 1,6V is enough. 

I don't think so
Probably these measurements was done at 0.1C
And even these measurements gives as a very tiny reserve of 20 mV. (Atmega's ADC step is about 30mV)

Ok.. How about.. 0.3C?
My new batteries hits 1.52V
6YO - 1.611-1.623

[Владимир Залогин]

Yes measurements were made at 0,1С. Agree with you, be better if default set in profile NIMH - charging current = 0,3C, but not C.

четверг, 12 февраля 2015 г., 20:24:21 UTC+3 пользователь Igon написал:

[Igon]

Владимир I am talking about voltage limit, not about defaults for charging current.

  I mean the limit 1,6V is enough. 

I don't think so

 

Pawel can you please look closer at NiMH upper limit?

It directly affects the operation of the charger..
(in contrast to the lower limit for lead batteries which may degrade or may not degrade capacity)

[Paweł Si]

2015-02-13 19:06 GMT+01:00 Igon <igg...@gmail.com>:

Владимир I am talking about voltage limit, not about defaults for charging current.

  I mean the limit 1,6V is enough. 

I don't think so

 

Pawel can you please look closer at NiMH upper limit?

It directly affects the operation of the charger..

Yes, I know that, I also have problems on some of my NiMH batteries,

this is the reason why I've added "Rwire" to "settings"

please see: https://github.com/stawel/cheali-charger/blob/master/docs/nimh_nicd_charging.md

but currently I'm not sure if a "upper limit setting" for NiMH and NiCd

wouldn't be a simpler solution,

Igon, please read the "nimh_nicd_charging" and let me know you opinion.

[SileNTViP SileNTViP]

суббота, 14 февраля 2015 г., 19:57:34 UTC+3 пользователь cheali-charger написал:

Maybe need to add +- to "upper limit for NiMH, NiCD" in settings? from 1.6 to 1.8

[Paweł Si]

2015-02-15 0:18 GMT+01:00 SileNTViP SileNTViP <silen...@gmail.com>:

Maybe need to add +- to "upper limit for NiMH, NiCD" in settings? from 1.6 to 1.8

Yes, exactly
I'm thinking about doing that, but I would like to know also Igons opinion on this

[Igon]

Hi Pawel

As I understand this situation - all our "high-voltage" NiMH batterys has a very big internal resistance - up to 0.5Ohm and more
So Wire resistance can be helpful sometimes but will not be effective solution..
(and it can't be precisely measured due to 30mV ADC resolution
Multimeter shows me 31.78mV voltage drop at 1A current while charger only 15-16)

Why do we use TYPICAL* charge voltage as an "Absolute Maximum Ratings" (limit / charge termination) which must not be reached?
*TYPICAL voltage - 1.55-1.6V it can be reached during process
1.55  - Duracell http://www6.zetatalk.com/docs/Batteries/Chemistry/Duracell_Ni-MH_Rechargeable_Batteries_2007.pdf
1.6  - Energizer http://data.energizer.com/PDFs/nickelmetalhydride_appman.pdf 

According to Atmel's manual?
How did they get 1.6V? At 1C current, at trickle current, without current? Also looks like they use intermittent charge like it was in original firmware.
(And I do not remember voltage settings for NiXX in it. Automatic determining the number of cells at battery with unknown condition doesn't looks plausible... Does it worked WITHOUT limits?)

[Paweł Si]

2015-02-15 14:30 GMT+01:00 Igon <igg...@gmail.com>:

Hi Pawel

As I understand this situation - all our "high-voltage" NiMH batterys has a very big internal resistance - up to 0.5Ohm and more
So Wire resistance can be helpful sometimes but will not be effective solution..
(and it can't be precisely measured due to 30mV ADC resolution
Multimeter shows me 31.78mV voltage drop at 1A current while charger only 15-16)

good point,

Why do we use TYPICAL* charge voltage as an "Absolute Maximum Ratings" (limit / charge termination) which must not be reached?
*TYPICAL voltage - 1.55-1.6V it can be reached during process
1.55  - Duracell http://www6.zetatalk.com/docs/Batteries/Chemistry/Duracell_Ni-MH_Rechargeable_Batteries_2007.pdf
1.6  - Energizer http://data.energizer.com/PDFs/nickelmetalhydride_appman.pdf

hmm... I also wondered from where I got the 1.6V limit 

I wrote the code about 2 years ago, so I don't remember anymore, 

but probably it's from wikipedia - I know, not the best place for reliable data.

According to Atmel's manual?
How did they get 1.6V? At 1C current, at trickle current, without current? Also looks like they use intermittent charge like it was in original firmware.
(And I do not remember voltage settings for NiXX in it. Automatic determining the number of cells at battery with unknown condition doesn't looks plausible... Does it worked WITHOUT limits?)

So what are You suggesting?

[Igon]

I think we can use Panasonic recommendation - "Charge terminating voltage - 1.8V/cell"
Other guides spoken about typical voltage only...

[Paweł Si]

2015-02-15 15:58 GMT+01:00 Igon <igg...@gmail.com>:

I think we can use Panasonic recommendation - "Charge terminating voltage - 1.8V/cell"
Other guides spoken about typical voltage only...

This would be the simplest solution, so I'm for it,

although adding a "volt. limit setting" is quit simple

maybe I should add this setting and set it to 1.8V as default?

(probably some people would be happier)

I could also remove the Rwire setting.

Are there any opposite views?

[Владимир Залогин]

Hello Igon!

I try to charge and discharge (format) NiMh battery with 0.3C current every step comes about 500 mA on 1,5A capacity of battery, but if i format battery with 0,1C current, it's 100-150mA, i give and take about 1500mA capacity.

Сonclusions NiMh battery necessary to charge current of about 0.1C, it is my opinion based on experience.

I think that it is necessary to set the default charging current is equal to NiMh 0,1-0,2C

четверг, 12 февраля 2015 г., 20:24:21 UTC+3 пользователь Igon написал:

 I charge and discharge 5 different capacity NIMH battery, charge all the stops to 1,58V 1,56V. All stops were dv = 5V. I mean the limit 1,6V is enough. 

[Igon]

Hello Владимир

I am not sure that I understood you correctly
Did you mean  -
at charging with 0.3C current - charge is 2000mAh  and discharge is 1500mAh
at 0.1C current - charge is 1600mAh discharge is also 1500mAh ?

[Владимир Залогин]

I mean that, when i charge the battery with capacity 1500mA with current 0.1C I have all 1500mA when discharge, and when i charge the same battery with current 0.3C i have only 500mA when discharge. Discharge current 200mA. In first way current of charge 150mA, in second way 500mA.

[Paweł Si]

2015-02-18 20:44 GMT+01:00 Владимир Залогин <zalog...@gmail.com>:

I mean that, when i charge the battery with capacity 1500mA with current 0.1C I have all 1500mA when discharge, and when i charge the same battery with current 0.3C i have only 500mA when discharge. Discharge current 200mA. In first way current of charge 150mA, in second way 500mA.

capacity is expressed in "mAh",

current in mA (or sometimes in this C notation).

what was the "charge complete, reason" ?

It was probably "V limit", this would indicate that our limit 1.6V per cell is to low.

[Владимир Залогин]

Hello Pawel!

I tested one battery NiMh marked as 2700mAh with real capacity 1500mAh (i know about mAh :-)

Result: First charge on current 100mA - it's (about 0.1C), till capacity become 2482mAh, reason of stop "dV"=-5mV. Then discharge  with current 200mA, with result 1508mAh.

Second charge on current 450mA - it's (about 0.3C), till capacity 1152mAh reason of stop "V limit"=1.6V. Then discharge  with current 200mA, with result 1290mAh.

среда, 18 февраля 2015 г., 23:52:57 UTC+3 пользователь cheali-charger написал:

[Paweł Si]

2015-02-20 17:58 GMT+01:00 Владимир Залогин <zalog...@gmail.com>:

Hello Pawel!

I tested one battery NiMh marked as 2700mAh with real capacity 1500mAh (i know about mAh :-)

Result: First charge on current 100mA - it's (about 0.1C), till capacity become 2482mAh, reason of stop "dV"=-5mV. Then discharge  with current 200mA, with result 1508mAh.

Second charge on current 450mA - it's (about 0.3C), till capacity 1152mAh reason of stop "V limit"=1.6V. Then discharge  with current 200mA, with result 1290mAh.

I did an update, now you can set  NiMH voltage limit in "settings"->"NiMH VCO: 1.800V"  (Voltage CutOff)

by default it's set to 1.8V and it's probably the best value.

[Владимир Залогин]

Hello Pawel and Igon!

It's done, good decision, everyone is happy. Thank you for a small voltage value NiMh profile for a charge. Another note, a change in capacitance NiMh profile, the value of the charging voltage increases as well as the capacity of the battery, but you can do to the value of the charging voltage, when changing value of capacity of batery, grow up with the value 0.3C, not 1C as now. And when i setup the value of the charging voltage, then i change any value i want.

пятница, 20 февраля 2015 г., 21:41:25 UTC+3 пользователь cheali-charger написал:

[Владимир Залогин]

And another proposal, i think option for NiMh battery, i mean "NiMH VCO" must setting in profile options "Edit battery" not in global option.

суббота, 21 февраля 2015 г., 14:32:11 UTC+3 пользователь Владимир Залогин написал:

[Igon]

Adjustable error level for NiXX? It will not be a very demanded option...

There is a problem with new options in "Edit battery" - no space in EEPROM
The only way is to reduce the number of battery's slots...

As for me, it would be great to see there triggers for determination whether to use the system's voltage shifts, aggressive discharge*, stops on disconnect or not while cycling**
* it can be useful for discharge NiXX time to time
** most of 2-cell protected DSLR's and walkie-talkie's batteries cannot be connected to balancer port and has a tendency to disconnects at full charge and discharge

dreams about System settings:
Separated capacity coefficients for different battery types
May be separated voltage shifts

[Paweł Si]

2015-02-21 20:22 GMT+01:00 Igon <igg...@gmail.com>:

Adjustable error level for NiXX? It will not be a very demanded option...

There is a problem with new options in "Edit battery" - no space in EEPROM

That's true 

The only way is to reduce the number of battery's slots...

actually it's not the only way,

we currently are using per battery:

1. 14 bytes for the batteries "name"

2. 12 bytes for battery info:  "type", "C", "Ic", "Id", nr of "cells", "time" limit

maybe we should remove the "name" and generate it at hoc?

the downside is that we will not be able to edit "name",

but I'm pretty sure nobody uses this functionality.

what do You think Igon?

but this is something for a future release,

I would like to finely release a stable version.

[SileNTViP SileNTViP]

maybe we should remove the "name" and generate it at hoc?

the downside is that we will not be able to edit "name",

but I'm pretty sure nobody uses this functionality.

what do You think Igon?

Generate name by battery param is good idea )

[Igon]

maybe we should remove the "name" and generate it at hoc?

the downside is that we will not be able to edit "name",

but I'm pretty sure nobody uses this functionality.

what do You think Igon?

It is a good thing (name)  and it will be a pity to refuse it...
But I never used it and most likely I won't use it in the future
So my vote is for releasing the space and using it for the new settings

[Владимир Залогин]

Hello Igon and Pawel!

So and how about idea, a change in capacitance NiMh profile, the value of the charging voltage increases as well as the capacity of the battery, but you can do to the value of the charging voltage, when i setting changing value of capacity of batery, grow up with the value 0.3C, not 1C as now. And when i setup the value of the charging voltage, then i change any value i want

понедельник, 23 февраля 2015 г., 16:40:14 UTC+3 пользователь Igon написал: